denver is hosting the debate and romney has been preparing there. the president has been preparing in nevada. both men will be very careful with everything they say, but some comments joe biden just made are putting the obama campaign on the defensive. >> how they can justify raising taxes on the middle class that's been buried the last four years. >> we agree. that means we need to stop digging by electing mitt romney the next president of the united states. >> biden later tried to clarify his comment by saying the middle class was buried by policies mitt romney and paul ryan supported. >>> tonight's debate comes as the race for president tightens a bit. president obama leads mitt romney by 3% among likely voters in the latest increaspoll. that is within the margin of error. the president led his republican rival by five percentage points two weeks ago. he had a widen lead if you consider registered voters. president obama leads romney by 7% in that category. you can watch tonight's debate right here on nbc 4. nbc news live team coverage begins at